Nano shower for chip-scale cooling

ABSTRACT

A nano shower cools a chip when a coolant sprays onto the chip package from an array of electro spray nozzles. Ideally, the coolant is not conductive and otherwise not harmful to electronics. As such, perfluorocarbons are ideal coolants. Distilled water also works in certain applications. A voltage difference between the coolant and chip package causes the coolant to spray from the electro spray nozzles onto the chip package. The coolant cools the chip package by evaporating or by absorbing heat and flowing away.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims the priority and benefit of U.S. Provisional Patent Application No. 60/949,464 filed on Jul. 12, 2007 entitled “NANO SHOWER FOR CHIP-SCALE COOLING” and which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments relate to semiconductor chips, semiconductor chip packaging, and evaporative cooling.

BACKGROUND OF THE INVENTION

Semiconductor chips perform remarkable feats but also generate heat. In general, increased performance requires increased power consumption and the consumed power is almost completely converted into heat. Two methods are used to minimize heating effects. Low power design leads to lower power consumption and less heat. Heat can also dissipated before the chip gets so hot that it fails. To increase heat dissipation, heat can be conducted from the semiconductor chip to a heat sink. The heat sink is usually a metallic piece in physical contact with the semiconductor chip or the chip's packaging. The heat sink typically has fins or a similar structure to increase surface area and thereby the heat flow from the heat sink to the local environment. A fan can also be used to drive air past the semiconductor chip or heat sink to further increase the flow of heat into the environment.

One type of liquid cooling is a technique whereby a liquid flows through the heat sink and carries away heat. Water is commonly used because it is inexpensive and abundant.

Another type of liquid cooling is immersion cooling. The entire subsystem containing the semiconductor chip can be submersed into a liquid. Heat flows into the liquid. Cooling the liquid also cools the semiconductor chip. Special liquids that do not conduct electricity or corrosion are required for immersion cooling. Those liquids include distilled water and perfluorocarbons. FC-72 and FC-77 are examples of perfluorocarbons that are available and used as electronics coolant liquids.

Packaging and heat dissipation constraints for some electronics systems preclude the use of most semiconductor cooling technologies. As such, these systems are limited to low power designs. Systems and methods for cooling such systems are required so that higher power systems can be employed.

BRIEF SUMMARY

The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments and is not intended to be a full description. A full appreciation of the various aspects of the embodiments can be gained by taking the entire specification, claims, drawings, and abstract as a whole.

It is therefore an aspect of the embodiments that an array of electro spray nozzles receives coolant that has a first voltage. A chip package is maintained at a different voltage to create a voltage difference between the coolant and the chip package. As such, the voltage difference causes the coolant to spray from the electro spray nozzles onto the chip package. The chip package is cooled as the coolant evaporates, flows away, or both. Cooling the chip package also cools a chip, such as a powered semiconductor chip, within the chip package.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer to identical or functionally similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate aspects of the embodiments and, together with the background, brief summary, and detailed description serve to explain the principles of the embodiments.

FIG. 1 illustrates a system for spraying coolant 102 onto a chip package 107 in accordance with aspects of the embodiments; and

FIG. 2 illustrates high level flow diagram of cooling a chip with a coolant sprayed from electro spray nozzles in accordance with aspects of the embodiments.

DETAILED DESCRIPTION

The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. In general, the figures are not to scale.

A nano shower cools a chip when a coolant sprays onto the chip package from an array of electro spray nozzles. Ideally, the coolant is none corrosive bu with high evaporative enthalpy. As such, perfluorocarbons are ideal coolants. Distilled water also works in certain applications. A voltage difference between the coolant and chip package causes the coolant to spray from the electro spray nozzles onto the chip package. The coolant cools the chip package by evaporating or by absorbing heat and flowing away.

FIG. 1 illustrates a system for spraying coolant 102 onto a chip package 107 in accordance with aspects of the embodiments. The coolant 102 can be held in a reservoir 103 from which it is supplied to electro spray nozzles 101. A power supply 105 can create a voltage difference between the coolant 102 and a chip package 107. Wires 104, 106 can connect the power supply 105 to the chip package 107 and coolant 102. The voltage difference causes the coolant 102 to spray from the electro spray nozzles 101 onto the chip package 107. A chip 108 inside the chip package 107 is cooled when the chip package 107 is cooled.

The chip package can be a multi chip module containing many chips. The chip package can also be a bare chip protected from the environment by little more than a passivation layer as is commonly used in semiconductor processing. The chip, or chips, can be powered semiconductor chips such as processors and memory. Wires 109, 110 from a power supply 111 can power the chip 108 inside the chip package 107.

The cooling effect occurs when the coolant conducts heat away from the chip package. One way this occurs is when the coolant evaporates. Another is when the coolant flows away from the chip package 107. A channel 113 such as a tube, trough, or trench can help direct the flow of coolant 102. As illustrated, nano shower 114 is directed vertically onto the chip package 107. Due to the voltage difference, the nano shower 114 can be directed horizontally or even upwards. As such, the chip package can be arranged vertically or in some other orientation to direct the coolant 102 flow.

Notice that the cooling can be produced by any power source that produces a voltage difference. A power supply plugged into the electrical grid or a similar source can be a power source as can a battery.

A spacer 112 can establish a gap between the electro spray nozzle array and the chip package. The spacer 112 can incorporate holes or channels so that evaporated or flowing coolant can carry heat away from the chip package 107. Alternatively, the spacer can consist of multiple separate pieces such as posts, beads, or fibers that maintain the gap while allowing coolant to escape from the gap. Posts, beads, and fibers have been used to create gaps in flat panel displays.

In one specific embodiment an array of electro spray nozzles can consist of holes of approximately 1 micron diameter with a density of approximately 10,000 nozzles per square centimeter. Numerous known fabrication methods can produce such an array. For example, photolithography followed by etching or laser drilling can produce suitable electro spray arrays. A 10 volt difference between the coolant and the chip package can cause a coolant such as water to spray from the nozzles onto the chip package. The distance between the nozzles and chip package can be less than a millimeter with 0.2 millimeter being the gap in the embodiment currently being described. Under these conditions, each nozzle can flow 2 micro liters per minute such that 1 square centimeter of nozzles produces a 20 milliliter coolant flux. As such, cooling with water that evaporates on the chip package surface can yield over 600 Watts of cooling per square centimeter.

FIG. 2 illustrates high level flow diagram of cooling a chip with a coolant sprayed from electro spray nozzles in accordance with aspects of the embodiments. Upon starting 201 coolant is supplied to a reservoir 202 such that the coolant passes into the electro spray nozzles 203. A voltage difference is established between the coolant and the chip package 204 thereby causing the coolant to spray onto the chip package 205. The coolant evaporates or flows away thereby cooling the chip 206. The process is continuous while cooling is desired 207. The process is done 208 when cooling is no longer desired.

It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. 

1. A system comprising: a plurality of electrospray nozzles; a coolant; and a means of creating a voltage difference between the coolant and a chip package wherein the chip package comprises a chip; wherein the potential difference drives the coolant through the electro spray nozzles and onto the chip package to thereby cool the chip.
 2. The system of claim 1 wherein the coolant cools the chip by evaporating.
 3. The system of claim 1 wherein the coolant cools the chip by absorbing heat and flowing away from the chip.
 4. The system of claim 1 wherein the coolant comprises a perfluorocarbon.
 5. The system of claim 1 wherein the coolant comprises water.
 6. The system of claim 1 wherein the means of creating a voltage potential difference is a power supply.
 7. A system comprising: a plurality of electrospray nozzles; a coolant reservoir wherein a coolant in the reservoir passes to the electrospray nozzles; and a means of creating a voltage difference between the coolant and a chip package comprising a chip; wherein the potential difference causes the coolant to spray onto the chip package to thereby cool the chip; and wherein the chip is a powered semiconductor chip.
 8. The system of claim 7 wherein the coolant cools the chip by evaporating.
 9. The system of claim 7 wherein the coolant cools the chip by absorbing heat and flowing away from the chip.
 10. The system of claim 7 wherein the coolant comprises a perfluorocarbon.
 11. The system of claim 7 wherein the coolant comprises water.
 12. The system of claim 7 wherein the means of creating the voltage potential difference is a power supply.
 13. The system of claim 7 wherein the coolant cools the chip by evaporating, wherein the coolant comprises a perfluorocarbon, wherein the coolant comprises water, and wherein the means of creating the voltage potential difference is a power supply.
 14. A method comprising: creating a voltage difference between a coolant and a chip package comprising a chip; wherein the coolant passes into a plurality of electrospray nozzles; wherein the voltage difference causes the coolant to spray from the electrospray nozzles onto the chip package; and wherein the chip is a powered semiconductor chip.
 15. The system of claim 14 wherein the coolant cools the chip by evaporating.
 16. The system of claim 14 wherein the coolant cools the chip by absorbing heat and flowing away from the chip.
 17. The system of claim 14 wherein the coolant comprises a perfluorocarbon.
 18. The system of claim 14 wherein the coolant comprises water.
 19. The system of claim 14 wherein the means of creating the voltage potential difference is a power supply.
 20. The system of claim 14 wherein the coolant cools the chip by evaporating, wherein the coolant comprises a perfluorocarbon, wherein the coolant comprises water, and wherein the means of creating the voltage potential difference is a power supply. 